Symmetrical sputtering apparatus with plasma confinement



July 29, 1969 w. v. RAUSCH E 3,458,425

SYMMETRICAL SPUTTERING APPARATUS WITH PLASMA CONFINEMENT I Filed May 25,1966 4 Sheets-Sheet l 1N VEN TQRS VV/L L MM ERA UJCH 1 y/4R THURCALDERONJR.

ATTQRNEYJ July 29, 1969 w. v. RAUSCH ET AL 3,458,426

' SYMMETRICAL SPUTTERI NG APPARATUS WITH PLASMA GONFINEMENT Filed May25, 1966 4 Sheets-Sheet 2 l N VliN '1 OR) I/V/L L MM V164 UJCH ART/10R(AL oERo/VJR.

AT ToR/vEKr y 969 w. v. RAUSCH ET AL 3,458,426

SYMMETRICAL SPUTTERING APPARATUS WITH PLASMA CONFINEMENT 4 Sheets-Sheet5 Filed May 25, 1966 IN vislvwm l/V/LL 1AM 14/64 use/4 BY ARTHURCALDERON Jk.

A T TORNE Kr y 9, 1969 w. v. RAUSCH ET AL SYMMETRICAIJ SPUTTERINGAPPARATUS WITH PLASMA GONFINEMENT Filed May 25, 1566 4 Sheets-Sheet 4 RU M mxm N HAD WRI. LKQ

MR Mu 5 MR United States Patent 3 458 426 SYMMETRICAL sPUTrERiNGAPPARATUS WITH PLASMA CONFINEMENT William V. Rausch, Minneapolis, andArthur Calderon,

Jr., Minnetonka, Minn, assignors to Fabri-Tek Incorporated, Edina,Minn., a corporation of Wisconsin Filed May 25, 1966, Ser. No. 552,917

Int. Cl. 'C23c 15/00 US. Cl. 204-298 19 Claims This invention isconcerned with deposition apparatus, and more particularly with improvedstructure for the deposition of thin films on substrate materials.

Conventional processes for the deposition of thin films use eitherthermal evaporation or low energy sputtering of the desired materialswith subsequent condensation of the sputtered material on a glass orother material substrate.

These two methods have various advantages and disadvantages, well knownto those skilled in the art. One of the primary limitations of bothmethods has been the inability to deposit uniform films over very largesubstrate areas, which would reduce the individual substrate cost. Theapparatus of this invention enables low energy sputtering whereby alarge number of substrates can be processed in a single cycle ofoperation, thus reducing the individual substrate cost whilesimultaneously maintaining or improving the composition control, filmthickness uniformity, and deposition rate. These improvements are madepossible by a cylindrical arrangement of the sputtering fixtures, byincorporating symmetry of the fixture arrangement, and by utilizing amagnetic field for control of the sputtered plasma. The magnetic fieldis also used as an orienting field when thin film magnetic memoryelements are deposited. Prior art sputtering apparatus has generallybeen of a planar arrangement or with a rodshaped target with substratesheld on each of four sides of the target.

Briefly described, the apparatus of this invention comprises adeposition chamber formed by a cylindrical jar. Upper and lower platesare attached to the jar, and each of the upper and lower plates carriesapparatus for evacuating the chamber, filament members, apparatus forinserting the gas into the evacuated chamber, and feedthroughs forvarious electrical, mechanical and cooling apparatus used in thedeposition process. A pair of modified Helmholtz coils are wound aroundthe outside of the cylindrical jar, including a control coil connectedbetween the pair. A plasma restrictor is mounted inside and arouind thelongitudinal axis of the deposition chamber. An annular anode member ismounted substantially at the center of the chamber, around andtransverse to the plasma restrictor. The anode member substantiallydivides the chamber into an upper and a lower section. Mounted in theupper and lower sections, in substantial mirror symmetry around theanode member, are a pair of cylindrical target members, a pair ofcylindrical control target mem bers, a pair of right polygonal prismshaped substrate holders, and pairs of substrate heating and coolingapparatus.

The mirror symmetry around the annular anode, and the substantiallycylindrical shape of the substrate holder, that is the right polygonalprism shape, enable the deposition of films on a high plurality ofsubstrates during a single evacuation cycle. Further, the use of theplasma restrictor and the magnetic field set up by the Helmholtz coilspromotes etficient control of the plasma available for deposition.

In the drawings:

FIG. 1 is a planar external view of an embodiment of the depositionapparatus of this invention;

3,458,426 Patented July 29, 1969 ice FIG. 2 is a sectional view takenalong the section line 2--2 of FIG. 1;

FIG. 3 is an enlarged view of a portion of the drawing of FIG. 2;

FIG. 4 is an orthographic view of a substrate holder forming a portionof the apparatus of this invention;

FIG. 5 is a schematic representing the electrical connections of thesputtering apparatus of the embodiment of this invention; and

FIG. 6 is a schematic representing the electrical interconnection ofmagnetic coils used in the apparatus of this invention.

In FIG. 1 there is shown a cylindrical jar 10, covered at one end by aplate 11, and covered at the other end by a plate 12. Plate 12 isconnected through a throat 17 to a flange connection 14. Flangeconnection 14 is also connected to a member 15 containing baffies andvalves. Member 15 is connected to a diffusion pump 16. Plate 11 isconnected through a throat 18 to a flange connection 19. Flangeconnection 19 is also connected to a member 21 containing battles andvalves. Member 21 is connected to a diffusion pump 22. Three magneticcoils 24, 25 and 26 are shown wound around jar 10.

In FIG. 2 there is shown a sectional view of jar 10, including coils 25and 26, plate 12, and a portion of throat 17. It can be seen that theconnection of jar 10 and plate 12 is sealed by an L-seal gasket 13.Within jar 10, there are shown a pair of plates 28 and 29, mounted inparallel spaced relation on plate 12 by a plurality of bolts such as 31and 32. Mounted on plate 29' is a plasma restrictor 30, here shown inthe form of a sealed glass cylinder. Mounted on plate 28 is an annularradiation shield 34, and within shield 34 is mounted a circular filament35. A set of cooling coils 38 is mounted below plate 28.

There is also shown mounted on plate 28 a shutter 37, here shown as amovable or telescoping shutter. A tube 39 is shown passing throughthroat 17 and having one end opening into jar 10. The other end of tube39 is connected to a source of gas, such as a noble gas (not shown).Immediately surrounding plasma restrictor 30, there is shown asymmetrical primary target 41. Around target 41 there is shown a helicalcontrol target 42. Around target 42 there is shown a substrate holder45. Around substrate holder 45 there is shown a cylindrical substrateheater 46, and helically wound around 46 there are shown cooling coils48.

Also shown, substantially at the center of the chamber formed by jar 10,is an annular anode 50 around plasma restrictor 30. Above anode 50,there are shown mounted a portion of further deposition apparatus,substantially in mirror symmetry to the above described apparatus whichis mounted below anode 50. The further apparatus is represented by aprimary target 51, a helical control target 52, a substrate holder 55, asubstrate heater 56 and cooling coils 58.

It is to be understood that plate 11, though not shown in the drawingsof FIGS. 2 and 3 carries substantially the same equipment as that showncarried by plate 12, including an upper portion of plasma restrictor 30.Thus plate 11 would carry another filament, another filament radiationshield, another telescopic shutter, and another tube from a source ofgas. In throat 17 there is shown mounted a valve 59 for varying theamount of vacuum pressure from diffusion pump 16 shown in FIG. 1.

Referring now to FIG. 3, there is shown an enlarged sectional view of aportion of the apparatus of FIG. 2. Again there is shown jar 10 havingwound thereon coils 25 and 26, mounted on plate 12, and sealed by gasket13. This enlarged view more clearly shows the spaced relation of thevarious deposition apparatus including filament 35 in shield 34, shutter37, primary target 41,

control target 42, substrate holder 45, substrate heater 46, and coolingcoils 48. There is also shown a feedthrough 61 in plate 12 through whichvarious electrical, mechanical and cooling inputs are fed to the properapparatus.

In FIG. 4 there is shown an orthographic view of substrate holder 45. Itcan be seen in FIG. 4 that holder 45 is in substantially the form of aright polygonal prism, which is in itself substantially cylindrical, andis especially suitable for holding a plurality of substrates. The numberof sides of the polygonal prism of FIG. 4 is merely exemplary of thesubstrate holder of this invention, and it is not intended that theapparatus of this invention be limited to the particular polygonal prismshown.

In FIG. 5 there is shown an electrical wiring diagram disclosing theinterconnections of the filaments, anode, and targets of this invention.A source of AC power 65 is connected across filament 35 which is mountedon plate 12. One end of filament 35 is connected to a common ground.Another source of AC power 66 is connected across a filament 36 which ismounted on plate 11. One end: of filament 36 is also connected to thecommon ground.

A variable source of DC power 70 is shown having a positive terminalconnected to anode 50'. A negative terminal of source 70 is connectedthrough a variable impedance 71 to cylindrical primary target 41. Thenegative terminal of source 70 is connected through a variable impedence72 to cylindrical primary target 51. A variable source of DC power 75 isshown having a positive terminal connected to anode 50. Source 75 has anegative terminal connected through a variable impedance 76 to helicalcontrol target 42. The negative terminal of source 75 is connectedthrough a variable impedance 77 to helical control target 52. Thepositive terminal of source 75 is connected through a resistor 81 and avariable source of DC power 80 to the common ground. The dotted lines 63of FIG. 5 represent the plasma field set up in the chamber formed by jar10.

In FIG. 6 magnetic coils 24 and 26 are shown serially connected across asource of DC power 84. Control coil 25 is shown connected across anothersource of DC power 83.

From the above discussion of FIGS. 1-6 and the physical relations of theapparatus shown therein, it will be apparent that the apparatus of thisinvention possesses double or mirror image symmetry with respect to animaginary plane passed through annular anode 50, as seen best in FIG. 2.This symmetry is particularly advantageous because it allows depositionon twice as many substrates, while simultaneously, when used inconjunction with the variable magnetic field set up by coils 24, 25 and26, and with plasma restrictor 30, it maintains uniformity of filmthickness and deposition rate.

For a better understanding of the operation of the apparatus of thisinvention, it should be understood that in normal engineeringterminology the process called low energy sputtering specifically meansthe degradation of a surface by ionic bombardment. Deposition bysputtering refers to the removal of target or source material byimpinging gas ions, generally noble gas, and subsequent condensation ofthis material upon substrates.

Primary targets 41 and 51 may be composed of a standard alloy. Controltargets 42 and 52, which are here shown as helical but may be a mesh orthe like, surrounding the respective primary targets 41 and 51, can beof a similar composition with a variance in the ratio or percent of thealloy materials. With reference to FIG. 5, cylindrical primary targets41 and 51 are maintained at a negative voltage by variable source 70.Variations of the voltage determine, to some extent, the sputteringrates of the alloy of targets 41 and 51, which are the primary source ofthe deposited alloy material. Helical control targets 42 and 52 aremaintained at a negative voltage somewhat less than the potential ofprimary targets 41 and 51, by source 75. This voltage determines thesputtering rate of the alloys of the control targets. Proper adjustmentof sources 70 and will allow deposition of films of compositions withina range determined by the alloys of the primary and control targets. Aparticular composition of film may be determined experimentally. Thiscontrol over the resultant film composition is highly desirable, ascommercially available high purity alloys of precise composition areprohibitively expensive for most practical thin film devices. Most anydesirable alloy film can be deposited using the apparatus of thisinvention.

In particular, magnetic thin films used for high speed computer memoriesmust exhibit a property called uniaxial anisotropy. that is, the filmsmust have an easy and a hard axis of magnetization. This anisotropicproperty is induced in magnetic films by the magnetic field supplied bythe modified Helmholtz coils 24 and 26. These coils, in conjunction withcontrol coil 25, and plasma restrictor 30, are also used to control thedensity and density-variation of the plasma.

Referring to FIG. 6 it will be apparent that modified Helmholtz coils 24and 26 are independently energized by source 84. The distance betweencoils 24 and 26 is mechanically variable, and this distance, inconjunction with the current in control coil 25, which is separatelyenergized by source 83, and the currents in coils 24 and 26, willdetermine the shape of the resultant magnetic field. In general, if thedistance between coils 24 and 26 is equal to their radius, the magnitudeof the field at the anode end of primary targets 41 and 51 isapproximately one-half of the magnitude of the field at the filament endof the primary targets. This variation of magnetic field magnitude willtend to pinch or reflect the plasma 63 toward the anode end of targets41 and 51, thus reducing the ion density gradient. It is necessary thatthe density of the plasma in the area of targets 41 and 51 be uniform ifuniformity of thickness of the resultant films is to be maintained.Control coil 25 is energized for additional control over the shape ofthe magnetic field. This controls the plasma density distribution,because the magnetic field from control coil 25 will tend to increasethe field magnitude at the anode end of targets 41 and 51 to a greaterextent than at the filament end of targets 41 and 51. The spacingbetween coils 24 and 26, the current in coils 24 and 26, and the currentin coil 25 can be established for optimum film thickness uniformity byexperiment. Once these factors are established, the average density ofplasma 63 in the target area can be controlled.

While maintaining the ratio of the currents in coils 24 and 26, and coil25, to assure film thickness uniformity, the magnitude of the magneticfield in the area of targets 41, and 51 is varied by varying thecurrents in coils 24, 25 and 26. Note that the optimum ratio of thesecurrents is maintained a constant regardless of current magnitudes.Because the cylindrical plasma restrictor 30 inhibits gas ionization atthe center of the chamber formed by jar 19, increases in currents inHelmholtz coils 24 and 26, and control coil 25, will tend to compressthe plasma 63 in the target area, thus increasing the average density ofplasma 63 while maintaining uniformity of the density. The sputteringrate is a function of the plasma density, therefore, the currentsettings for optimum deposition rates are determined experimentally foreach material to be deposited. The sputtering rate is also a function oftarget voltage, which must be considered simultaneously.

Assuming that optimum primary and control target voltages, and optimumplasma density variation, have been established as described above, thedeposition procedure can be commenced. First, substrates are firmlymounted on substrate holders 45 and 55. The vacuum chamber in jar 10 isthen sealed, pumps 16 and 22 are turned on, and the chamber pumped downto a high degree of vacuum (for example, 10 mm. Hg or less). Substrateheaters 46 and 56, and filaments 35 and 36, are energized sufficientlyto out-gas impurities. Filament power, by means of sources 65 and 66, isthen increased for optimum thermionic emission from filaments 35 and 36,and the filament temperature is stabilized. A positive potential is thenapplied to anode 50. Note source 80 of FIG. 5, and also note thatfilaments 35 and 36 are connected to the common ground.

With the positive potential on anode 50, valve 59 in throat 17, and asimilar valve in throat '18, are moved to throttle down the vacuum pumpinlet. A gas, usually a noble gas such as argon, is bled in through tube39 and a similar tube in plate 11, at a flow rate substantially equal tothe throttled pumping rate. These rates are adjusted such that the gaspressure in the chamber formed by jar is, for example, 1 to 10 microns.Under these conditions, thermionically emitted electrons ionize thenoble gas atom by collision in transit to anode 50 from filaments 35 and36, and a dense plasma 63 is initiated. Large potentials, negative withrespect to anode 50, are then applied to primary targets 41 and 51 andcontrol targets 42 and 52. The targets then act like large negativeLangmuir probes, immersed in the plasma, and space charge sheaths areformed adjacent to the various target surfaces. The positive ions of theplasma are accelerated through the space charge sheaths and as theyimpinge on the target surfaces, sputtering occurs. During the entireabove described operation, shutter 37, and a similar shutter attached toplate 11, are extended to cover substrates on substrate holders 45 and55. Thus, as the ions impinge on the target surfaces, the targets aresputtered clean, with the shutters such as 37 shielding the substrates.

When adequate time has been allowed for removal of the contaminatingsurface layer on the targets, shutter 37 and the corresponding shutterin plate 11 are removed to allow the sputtered particles to be depositedon substrates held by substrate holders 45 and 55. If desired, a higherpotential may be used during cleaning to speed up the decontaminationprocess.

The number of sputtered atoms per impinging incident ion is proportionalto the energy of the impinging ion for the normal operating targetpotentials. This energy is very nearly determined by the potentialbetween targets 41, 51, 42, and 52 and anode 50. Thus, the compositionof the resulting deposited film can be controlled by merely adjustingtarget voltages.

It should be noted that cylindrical plasma restrictor 30 is sealed, thusreducing the volume of gas that must be pumped into jar 10 during eachdeposition cycle and thus improving the over-all economic efiiciency ofthe apparatus of this invention. Further, the only major limitation onthe size of the apparatus of this invention, and thus the number ofsubstrates available for deposition during each cycle, would be themechanical construction and electrical isolation problems. Cooling coils48 and 58, which surround, respectively, substrate heater assemblies 46and 56, serve the double function of minimizing the amount of radiantenergy reaching jar 10, and rapidly cooling the deposition apparatusafter completion of a deposition cycle.

From the above description of the structure and operation of theapparatus of this invention, it is apparent that the use of an annularanode, around which deposition apparatus is placed in substantial mirrorsymmetry, and the use of a centrally located plasma restrictor todecrease the volume of the deposition chamber, along with the use ofmagnetic fields, results in efiicient and high quality depositionapparatus which allows the deposition of films on substrates withgreater quality control and significantly lower cost.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:

1. Apparatus for the deposition of films on a substrate comprising:

a vacuum chamber;

evacuating means connected to said vacuum chamber;

anode means mounted within said vacuum chamber and substantiallydividing said vacuum chamber into an upper chamber and a lower chamber;

first and second filament means mounted, respectively, in said upper andlower chambers and in substantial mirror symmetry;

first and second target means mounted, respectively, in said upper andlower chambers and in substantial mirror symmetry;

first and second substrate holding means mounted, re-

spectively, in said upper and lower chambers and in substanital mirrorsymmetry;

first and second movable shutter means mounted, re-

spectively in said upper and lower chambers and in substantial mirrorsymmetry;

filament power supply means connected to each of said filament means;

target power supply means;

means connecting said target power supply means and said anode means inelectrical circuit with each of said target means;

means mounted adjacent said upper and lower chambers for creating amagnetic field generally parallel to the axis of the discharge therein;

a source of gas particles and means for directing said gas particlesinto said vacuum chamber; and

said gas particles becoming ionized in said vacuum chamber to impingeupon said target means for sputtering metal particles ofi said targetmeans for deposition on substrates mounted on said substrate holdingmeans, said shutter means shielding the substrates until said targetmeans are sputtered clean and then moving to allow deposition on thesubstrates.

2. The apparatus of claim 1 including:

first and second control target means mounted, respectively, in saidupper and lower chambers and in substantial mirrer symmetry.

3. The apparatus of claim 1 in which:

said vacuum chamber has cylindrical walls;

said filament means are circular;

said target means are cylindrical and mounted with the longitudinal axissubstantially on the vacuum chamber longitudinal axis; and

said substrate holding means are substantially right polygonal prismsand mounted with the longitudinal axis substantially on the vacuumchamber longitudinal axis, surrounding and in spaced relation to therespective target means.

4. The apparatus of claim 3 including:

first and second cylindrical control target means;

control target power supply means;

means connecting said control target power supply means and said anodemeans in electrical circuit with each of said control target means; and

said first control target means mounted in said upper chamber betweenand in spaced relation to said first target means and said firstsubstrate holder means;

said second control target means mounted in said lower chamber betweenand in spaced relation to said second target means and said secondsubstrate holder means.

5. The apparatus of claim 3 including:

first and second annular shield means mounted, respectively, around saidfirst and second filament means.

6. The apparatus of claim 3 in which said movable shutter means aretelescopic and are mounted to shield the substrates on the respectivesubstrate holder means from the respective target means in the extendedposition.

7. The apparatus of claim 3 in which said means for creating a magneticfield in said vacuum chamber compr1se:

a pair of modified Helmholtz coils wound around the cylindrical walls ofsaid vacuum chamber, in spaced relation to one another;

a first source of energy;

said pair of coils and said first source of energy connected inelectrical circuit;

a control coil wound around the cylindrical walls of said vacuum chamberbetween said pair of coils; and

a second source of energy connected in electrical circuit with saidcontrol coil.

8. The apparatus of claim 3 including:

first and second substrate heater means mounted, respectively, adjacentsaid first and second substrate holder means; and

cooling means mounted adjacent each of said substrate heater means andsaid filament means.

9. The apparatus of claim 3 in which said anode means is annular.

10. The apparatus of claim 9 including:

a cylindrical plasma restrictor mounted with the longitudinal axis alongthe longitudinal axis of said vacuum chamber and mounted within saidannular anode means and said first and second cylindrical target means.

11. Apparatus for deposition of films by sputtering comprising:

a cylindrical vacuum chamber;

an annular anode mounted in said vacuum chamber, the plane of said anodesubstantially dividing said vacuum chamber into a first chamber and asecond chamber;

a cylindrical plasma restrictor mounted within said vacuum chamber andextending through said annular anode, the longitudinal axis of saidrestrictor being the longitudinal axis of said vacuum chamber;

first and second cylindrical targets mounted, respectively, in saidfirst and second chambers, the radius of said targets being greater thanthe radius of said restrictor, and the longitudinal axes of said targetsbeing the longitudinal axis of said vacuum chamber;

first and second substrate holders in the form of right polygonal prismsmounted, repectively, in said first and second chambers, the radius ofsaid holders being greater than the radius of said targets, and thelongitudinal axes of said holders being the longi' tudinal axis of saidvacuum chamber;

first and second cylindrical movable shutters mounted, respectively, insaid first and second chambers, the radius of said shutters beinggreater than the radius of said targets and less than the radius of saidholders, and the longitudinal axes of said shutters being thelongitudinal axis of said vacuum chamber;

first and second circular filaments mounted, respectively, in said firstand second chambers, the axes of said filaments being the longitudinalaxis of said vacuum chamber;

means for providing a magnetic field in said vacuum chamber;

means connecting each of said targets and said filaments in electricalcircuit with said anode;

evacuation means connected to said vacuum chamber;

a source of gas particles; and

means for providing said gas particles into said first and secondchambers for ionization thereof to provide a plasma of ionized particlesfor sputtering of said targets.

12. The apparatus of claim 11 including:

first and second cylindrical control targets mounted, respectively, insaid first and second chambers, the radius of said control targets beinggreater than the radius of said targets and less than the radius of saidshutters, and the longitudinal axes of said control targets being thelongitudinal axis of said vacuum chamber.

13. The apparatus of claim 12 in which said means for providing amagnetic field comprises:

first and second magnetic coils mounted in spaced relation around theexternal periphery of said cylindrical vacuum chamber, said coilsconnected in electrical circuit; and

a control coil connected in electrical circuit and mounted between saidfirst and second coils around the external periphery of said cylindricalvacuum chamber.

14. Deposition apparatus comprising:

means defining a vacuum chamber;

anode means mounted in the chamber;

first and second filaments means mounted in the chamber in spacedrelation and one on each side of said anode means;

first deposition means including target and substrate holder meansmounted in the chamber between said first filament means and said anodemeans;

second deposition means including target and substrate holder meansmounted in the chamber between said second filament means and said anodemeans;

means for providing gas particles into the chamber;

and

means connected to said anode, filament and target means for ionizingsaid gas particles in the chamber to sputter material off said targetmeans for depositon on substrates held by said substrate holder means.

15. The apparatus of claim 14 including:

plasma restrictor means mounted in the chamber for decreasing the volumethereof, to increase the density of ionized gas particles.

16. The apparatus of claim 15 in which:

said anode means is annular in shape and mounted around said plasmarestrictor.

17. The apparatus of claim 14 in which said first and second meansinclude, respectively:

first and second movable shutter means for selectively shieldingsubstrates on said substrate holder means from the sputtered material.

18. The apparatus of claim 17 in which:

said first and second deposition means are in substantial mirrorsymmetry about the plane of said anode means.

19. The apparatus of claim 14 including:

means for providing a magnetic field generally parallel to the axis ofthe discharge in the vacuum chamber, said means mounted on said meansdefining the vacuum chamber.

References Cited UNITED STATES PATENTS 3,293,168 12/1966 Schulz 204-192OTHER REFERENCES Bertelsen et al.: IBM Technical Disclosure Bulletin,vol. 6, No. 11, April 1964, p. 45.

HOWARD S. WILLIAMS, Primary Examiner SIDNEY S. KANTER, AssistantExaminer US. Cl. X.R.

14. DEPOSITON APPARATUS COMPRISING: MEANS DEFINING A VACUUM CHAMBER;ANODE MEANS MOUNTED IN THE CHAMBER; FIRST AND SECOND FILAMENTS MEANSMOUNTED IN THE CHAMBER IN SPACED RELATION AND ONE ON EACH SIDE OF SAIDANODE MEANS; FIRST DEPOSITON MEANS INCLUDING TARGET AND SUBSTRATE HOLDERMEANS MOUNTED IN THE CHAMBER BETWEEN SAID FIRST FILAMENT AND SAID ANODEMEANS; SECOND DEPOSITION MEANS INCLUDING TARGET AND SUBSTRATE HOLDERMEANS MOUNTED IN THE CHAMBER BETWEEN SAID SECOND FILAMENT MEANS AND SAIDANODE MEANS. MEANS FOR PROVIDING GAS PARTICLES INTO THE CHAMBER; AND